200 research outputs found
Quadrupole Moments of Neutron-Deficient Na
The electric-quadrupole coupling constant of the ground states of the proton
drip line nucleus Na( = 2, = 447.9 ms) and the
neutron-deficient nucleus Na( = 3/2, = 22.49 s)
in a hexagonal ZnO single crystal were precisely measured to be kHz and 939 14 kHz, respectively, using the multi-frequency
-ray detecting nuclear magnetic resonance technique under presence of an
electric-quadrupole interaction. A electric-quadrupole coupling constant of
Na in the ZnO crystal was also measured to be
kHz. The electric-quadrupole moments were extracted as Na) = 10.3
0.8 fm and Na) = 14.0 1.1 fm, using
the electric-coupling constant of Na and the known quadrupole moment of
this nucleus as references. The present results are well explained by
shell-model calculations in the full -shell model space.Comment: Accepted for publication in Physics Letters
Test of the Conserved Vector Current Hypothesis by beta-ray Angular Distribution Measurement in the Mass-8 System
The beta-ray angular correlations for the spin alignments of 8Li and 8B have
been observed in order to test the conserved vector current (CVC) hypothesis.
The alignment correlation terms were combined with the known beta-alpha-angular
correlation terms to determine all the matrix elements contributing to the
correlation terms. The weak magnetism term, 7.5\pm0.2, deduced from the
beta-ray correlation terms was consistent with the CVC prediction 7.3\pm0.2,
deduced from the analog-gamma-decay measurement based on the CVC hypothesis.
However, there was no consistent CVC prediction for the second-forbidden term
associated with the weak vector current. The experimental value for the
second-forbidden term was 1.0 \pm 0.3, while the CVC prediction was 0.1 \pm 0.4
or 2.1 \pm 0.5.Comment: 31 pages, 12 figures, Accepted for publication in Phys. Rev.
Fast switching NMR system for measurements of ground-state quadrupole moments of short-lived nuclei
A beta-ray detecting nuclear quadrupole resonance system has been developed
at NSCL/MSU to measure ground-state electric quadrupole moments of short-lived
nuclei produced as fast rare isotope beams. This system enables quick and
sequential application of multiple transition frequencies over a wide range.
Fast switching between variable capacitors in resonance circuits ensures
sufficient power delivery to the coil in the beta-ray detecting nuclear
magnetic resonance technique. The fast switching technique enhances detection
efficiency of resonance signals and is especially useful when the polarization
and/or production rate of the nucleus of interest are small and when the
nuclear spin is large
Quantum Monte Carlo calculations of nuclei
We report on quantum Monte Carlo calculations of the ground and low-lying
excited states of nuclei using realistic Hamiltonians containing the
Argonne two-nucleon potential alone or with one of several
three-nucleon potentials, including Urbana IX and three of the new Illinois
models. The calculations begin with correlated many-body wave functions that
have an -like core and multiple p-shell nucleons, -coupled to the
appropriate quantum numbers for the state of interest. After
optimization, these variational trial functions are used as input to a Green's
function Monte Carlo calculation of the energy, using a constrained path
algorithm. We find that the Hamiltonians that include Illinois three-nucleon
potentials reproduce ten states in Li, Be, Be, and B with
an rms deviation as little as 900 keV. In particular, we obtain the correct
3 ground state for B, whereas the Argonne alone or with
Urbana IX predicts a 1 ground state. In addition, we calculate isovector
and isotensor energy differences, electromagnetic moments, and one- and
two-body density distributions.Comment: 28 pages, 12 tables, 7 figure
Genetic linkage maps of Japanese and European pears aligned to the apple consensus map
Genetic linkage maps of the Japanese pear (Pyrus pyrifolia Nakai) cultivar `Housui¿ and the European pear (Pyrus communis L.) cultivar `Bartlett¿ were constructed based on Amplified Fragment Length Polymorphism markers (AFLPs), Simple Sequence Repeat markers (SSRs) (from pear, apple and Prunus), isozymes, and phenotypic traits by using their F1 progenies. The map of the female parent `Bartlett¿ consisted of 256 loci including 178 AFLPs, 76 SSRs (32 pear, 39 apple, 5 Prunus SSRs), 1 isozyme and a self-incompatibility locus on 19 linkage groups over a total length of 1020 cM. The map of `Housui¿ contained 180 loci including 110 AFLPs, 64 SSRs (29 pear, 29 apple, 6 Prunus SSRs), 2 phenotypic traits and 4 other markers on 20 linkage groups encompassing a genetic distance of 995 cM. These 2 pear maps were aligned using 37 co-dominant markers that showed segregating alleles in both parents. Out of 80 tested SSR markers developed from apple, more than four-fifth could produce discrete amplified fragments in pear. Thirty-eight apple SSR markers showed 39 segregating loci in the linkage map of `Bartlett¿, while 27 markers produced 29 loci in `Housui¿. All pear linkage groups could be successfully aligned to the apple consensus map by at least 1 apple SSRs, suggesting that positions and linkages of SSR loci were well conserved between pear and apple. The self-incompatibility locus (S locus) was mapped to linkage group 17 in Japanese and European pears as well as apple. Our results are the first major effort in comparative mapping of pear and appl
Measurement of the spin and magnetic moment of 23Al
For the first time, we obtained the g factor for the ground state of 23Al by use of a -NMR measurement. 23Al has a small proton separation energy and is a potential proton-halo candidate. The obtained g factor, |g|=1.557±0.088, clearly shows the spin and parity, J=5/2+, for 23Al, which is the same as that of its mirror partner, 23Ne. The possible nuclear structure of 23Al is also discussed
Precision measurement of the electric quadrupole moment of 31Al and determination of the effective proton charge in the sd-shell
he electric quadrupole coupling constant of the 31Al ground state is measured
to be nu_Q = |eQV_{zz}/h| = 2196(21)kHz using two different beta-NMR (Nuclear
Magnetic Resonance) techniques. For the first time, a direct comparison is made
between the continuous rf technique and the adiabatic fast passage method. The
obtained coupling constants of both methods are in excellent agreement with
each other and a precise value for the quadrupole moment of 31Al has been
deduced: |Q(31Al)| = 134.0(16) mb. Comparison of this value with large-scale
shell-model calculations in the sd and sdpf valence spaces suggests that the
31Al ground state is dominated by normal sd-shell configurations with a
possible small contribution of intruder states. The obtained value for
|Q(31Al)| and a compilation of measured quadrupole moments of odd-Z even-N
isotopes in comparison with shell-model calculations shows that the proton
effective charge e_p=1.1 e provides a much better description of the nuclear
properties in the sd-shell than the adopted value e_p=1.3 e
Why Are Outcomes Different for Registry Patients Enrolled Prospectively and Retrospectively? Insights from the Global Anticoagulant Registry in the FIELD-Atrial Fibrillation (GARFIELD-AF).
Background: Retrospective and prospective observational studies are designed to reflect real-world evidence on clinical practice, but can yield conflicting results. The GARFIELD-AF Registry includes both methods of enrolment and allows analysis of differences in patient characteristics and outcomes that may result. Methods and Results: Patients with atrial fibrillation (AF) and ≥1 risk factor for stroke at diagnosis of AF were recruited either retrospectively (n = 5069) or prospectively (n = 5501) from 19 countries and then followed prospectively. The retrospectively enrolled cohort comprised patients with established AF (for a least 6, and up to 24 months before enrolment), who were identified retrospectively (and baseline and partial follow-up data were collected from the emedical records) and then followed prospectively between 0-18 months (such that the total time of follow-up was 24 months; data collection Dec-2009 and Oct-2010). In the prospectively enrolled cohort, patients with newly diagnosed AF (≤6 weeks after diagnosis) were recruited between Mar-2010 and Oct-2011 and were followed for 24 months after enrolment. Differences between the cohorts were observed in clinical characteristics, including type of AF, stroke prevention strategies, and event rates. More patients in the retrospectively identified cohort received vitamin K antagonists (62.1% vs. 53.2%) and fewer received non-vitamin K oral anticoagulants (1.8% vs . 4.2%). All-cause mortality rates per 100 person-years during the prospective follow-up (starting the first study visit up to 1 year) were significantly lower in the retrospective than prospectively identified cohort (3.04 [95% CI 2.51 to 3.67] vs . 4.05 [95% CI 3.53 to 4.63]; p = 0.016). Conclusions: Interpretations of data from registries that aim to evaluate the characteristics and outcomes of patients with AF must take account of differences in registry design and the impact of recall bias and survivorship bias that is incurred with retrospective enrolment. Clinical Trial Registration: - URL: http://www.clinicaltrials.gov . Unique identifier for GARFIELD-AF (NCT01090362)
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